The Working Principle Of Three-Phase Asynchronous Motors

When a symmetrical three-phase alternating current is supplied to the three-phase stator windings, a rotating magnetic field is generated; this field rotates in a clockwise direction-at a synchronous speed *n1*-within the air gap between the stator and the rotor. Since the rotating magnetic field spins at speed *n1* while the rotor conductors are initially stationary, the rotor conductors cut through the stator's rotating magnetic field, thereby inducing an electromotive force (EMF) (the direction of which is determined by the Right-Hand Rule). Because the ends of the rotor conductors are short-circuited by end rings, the induced EMF drives an induced current through the rotor conductors, flowing in a direction essentially aligned with that of the induced EMF. These current-carrying rotor conductors then experience an electromagnetic force within the stator's magnetic field (the direction of this force is determined by the Left-Hand Rule). This electromagnetic force generates an electromagnetic torque acting on the rotor shaft, driving the rotor to rotate in the same direction as the rotating magnetic field.

Based on the analysis above, the operating principle of the motor can be summarized as follows: When a symmetrical three-phase alternating current is supplied to the motor's three-phase stator windings (which are electrically displaced by 120 degrees), a rotating magnetic field is produced. This rotating magnetic field cuts through the rotor windings-which form a closed circuit-thereby inducing currents within them. The current-carrying rotor conductors, under the influence of the stator's rotating magnetic field, generate electromagnetic forces; these forces create an electromagnetic torque on the motor shaft, driving the motor to rotate in the same direction as the rotating magnetic field.